Don't leave a trace: Private Browsing in Firefox
Today, a major feature was added to the pre-release versions of Firefox 3.1, called Private Browsing. I've been working for quite some time on this, so I thought it may be a good time to write about what this feature is and how to use it.
As you may know, while you browse the web, your browser usually records a lot of data which will later be used to improve your browsing experience. For example, it records a history of all the web pages you have visited, so that later if you need help remembering a site you visited a while back, it can assist you in finding that site. Now, that is great, but there is a downside: those data can be used to trace your online activities. For example, if your coworker sits at your computer, she can view all of your browsing history, which may not be what you want.
Suppose you're doing something online, and you don't want your coworkers know about it. An example scenario would be looking for a new employer while at work! One option would be to do your work, and then clear the data that Firefox has stored for you, such as history, cookies, cache, .... But the problem is that this action will also remove the parts of your online activities data which you don't want to hide, so the history that Firefox records can no longer be used to find a web site you had visited a month before. Private Browsing will help you here.
Private Browsing aims to help you make sure that your web browsing activities don't leave any trace on your own computer. It is very important to note that Private Browsing is not a tool to keep you anonymous from websites or your ISP, or for example protect you from all kinds of spyware applications which use sophisticated techniques to intercept your online traffic. Private Browsing is only about making sure that Firefox doesn't store any data which can be used to trace your online activities, no more, no less.
So how does one actually use this feature? It couldn't be simpler! To start, just select Private Browsing from the Tools menu.

You will see a dialog box which asks you whether you want to save and close all of your current windows and tabs, and start the Private Browsing mode. Click Start Private Browsing to start your private session.

After you do this, your non-private browsing session is closed and a new private session is opened, showing you the screen below. (Before you mention, the ugly icon you see there is something I created as a placeholder! This icon will be replaced in the final release of Firefox 3.1.)

As you see, not much is different in the Firefox window inside the Private Browsing mode, except for the (Private Browsing) text added to the title bar at the top of the window. That is intentional: after all, if you're doing something online that you don't want your coworkers to know about, you don't want to raise their attention with a big sign saying PRIVATE as they pass by and glance over your shoulder. 
At this stage, you can start browsing web sites, without ever having to worry that Firefox might store something on your computer which can be used to tell which pages you have visited. Once you're done, just uncheck the same menu item in the Tools menu to close your private session.

This action discards all of the data from your private session, and will restore your non-private browsing session, just like it was before entering the Private Browsing mode.

Now, as I mentioned at the top of this post, this feature is available in pre-release versions of Firefox 3.1 (what we geeks call nightly builds). This feature will be included in Firefox 3.1 Beta 2 which will be released soon, so if you want to try it, you can give it a shot then. And of course, it will appear in the final release of Firefox 3.1, so if you're not the type who test beta software, you can wait until Firefox 3.1 is released.
Update: As many people seem interested in knowing this, there is a way to make Firefox always start in Private Browsing mode. Go to the about:config page, click I'll be careful, I promise, type browser.privatebrowsing.autostart in the Filter text box, double click the entry to make its value true. After doing this, the next time you start Firefox, it will start in private browsing mode automatically. To turn this off, use the same steps to change the value of this preference to false. There is a plan to provide an easier method to set this option in the final release of Firefox 3.1.
Trackback URL for this post:
Privacy Solutions Series: Part 4 - Firefox Privacy Features
from The Progress & Freedom Foundation Blog on March 16, 2009 - 20:02By Adam Marcus As noted in the first installment of our "Privacy Solution Series," we are outlining various user-empowerment or user "self-help" tools that allow Internet users to better protect their privacy online-and especially to defeat tracking fo...
Mozilla firefox introduces private mode
from vijayjoshi.org on December 10, 2008 - 10:01Firefox users finally have the feature they were requesting for a long time. Pre-release of Firefox 3.1 Beta was done on 8th dec. This release includes, among many other features, an option to surf the web in Private mode.
This is similar to the Incogn...
firefox 3.1でプライバシーモード実装
from トランキの小部屋 on November 5, 2008 - 17:04先日google chromeのシークレットモードについてレポしましたが、firefoxの最新バージョン、3.1のベータ版で同様の機能を持つプライバシーモードが実...
Don't leave a trace: Private Browsing in Firefox
from Linux IT Consultant on November 5, 2008 - 05:15Today, a major feature was added to the pre-release versions of Firefox 3.1, called Private Browsing. I've been working for quite some time on this, so I thought it may be a good time to write about what this feature is and how to use it.
As you may ...

Comments
Pingback
[...] http://denverexpresscare.com/cheap-oil-changes-are-they-worth-it http://ehsanakhgari.org/blog/2008-11-04/dont-leave-trace-private-browsin... http://www.nodo50.org/markonidigital/b2pingbackspopup.php?p=4&pb=1 [...]
Pingback
[...] to the pre-release (developer) versions of Firefox 3.1, according to a blog post by Ehsan Akhgari: Don’t leave a trace: Private Browsing in Firefox. He also explains how to start Firefox in Private Browsing mode. However, as he says: Private [...]
Pingback
[...] Don’t leave a trace: Private Browsing in Firefox | Ehsan AkhgariAnd you’ll immediately see a private browsing window, which will leave no traces of your browsing history. Useful! … The other thing that private browsing is useful for is checking your email on somebody else’s computer – no danger of cookies lying around letting them back into your email account once you’ve gone. [...]
Pingback
[...] Don't leave a trace: Private Browsing in Firefox | Ehsan Akhgari 4 Nov 2008. For example, it records a history of all the web pages you have visited. To start, just select Private Browsing from the Tools menu... Mozilla Firefox 3 .1 Beta 2 Released « semuada.com - 2010-05-14 07:19 Don't leave a trace: Private Browsing in Firefox | Ehsan Akhgari [...]
Pingback
[...] [...]
private browsing!
would it be ok to get a private browsing in the title bar as someone mentioned up there?
Re: private browsing!
We already get "(Private Browsing)" in the title bar in Firefox 3.5 and 3.6.
Hello Ehsan Akhgari, I've
Hello Ehsan Akhgari,
I've used FF private browsing for internet banking for a long time, because I felt safer if *nothing* was written to disk on a PC dedicated to this task, though https traffic shouldn't already be saved.
Maybe, I misunderstood how FF PB works, but I saw a strange behavior in the latest FF versions (3.6.4 and 3.6.6).
Here what happens to me:
http://forums.mozillazine.org/viewtopic.php?f=38&t=1932683
Is a normal behavior?
I see a potential risk to privacy (and my bank account too), because I don't know *what* is being written to disk.
Re: Hello Ehsan Akhgari, I've
We make the promise of never writing anything to disc which can be used to identify the websites that you've visited inside private browsing mode. What kind of data are you actually talking about?
I can see via Windows Task
I can see via Windows Task Manager that FF has large disk activity when flash and other plugins' stuff is loaded in Private Browsing mode.
Previously, the FF process in the task manager didn't show such activity.
However, I've read this page:
http://www.adobe.com/devnet/flashplayer/articles/privacy_mode_fp10.1.html
and I suppose I've misunderstood how the plugins worked in the private browsing of previous FF versions.
Now, according to Adobe, at least Flash should *delete* whatever has *written* to disk, if in private browsing. A behavior taht is different from FF default, but equal to IE or other "private" mode.
I don't know if this is the reason why both "firefox.exe" and "plugin-container.exe" are showing disk activity in my task manager.
My Firefox version is a clean installation of 3.6.4 upgraded to 3.6.6 without any extension.
So far, nobody on Usenet and Mozillazine threads has confirmed this disk activity, so I don't know if it's normal or something strange happening on my system.
I've done a full test in
I've done a full test in private browsing mode and then checked FF cache and sql db with SQLite Browser and CacheViewer .
No cookie, image or other thing is written to FF cache.
Nevertheless, there is disk activity of both firefox.exe and plugin-container.exe. It seems it's really a Flash (plugin) issue.
I just need to know that this is the intended behavior on these FF versions.
Re: I've done a full test in
The mere presence of disk activity is not strange. Flash could be using the disk to store its information, and firefox.exe and plugin-container.exe might also use the disk to communicate back and forth with each other, but none of that should be counted as suspicious activity, unless you can see any files written on disk which include your browsing history information (such as the sites you've visited, etc.)
Thanks for your answer.
Thanks for your answer.
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
No PB external signs
I'm using FF 3.6.3 and wish there were only the internal one where Start changes to Stop Private Browsing in the Tools menu.
Re: No PB external signs
You should also get a "(Private Browsing)" in your title bar.
I'm sorry, I guess my wording
I'm sorry, I guess my wording did not make it clear. "No PB external signs" meaning to say I don't want it. I wish there were a way to remove it from the Title bar.
Re: I'm sorry, I guess my wording
Unforunately, there's currently no way to do that.
Re: Re: I'm sorry, I guess my wording
Thanks for your answer. Is there already in september any way to remove it from the Title bar?
there is no way
No there is already in october no way to remove it. Thanks a lot for your question!
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Private browsing for the Firefox deprived
The Firefox private browsing feature is great, but sometimes I have to use computers where Firefox is not installed. Here is an alternative, download and run ccleaner ( search "ccleaner").
It's a great little utility. Ummh, one thing though, while installing it will helpfully suggest an additional toolbar, but you can politely decline. So watch for it during installation.
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
How to delete effectively history from private search
Hello,
I used the private search and found no difficulties until recently. Now the history is shown when a site is repeated and when trying to clear it, only the public history search shows up for clearing and the private history remains untouchable. How to gain privated search history to then delete?
KK
I also used it
I have FF version 3.0 installed without this feature. All i can say, i just don't need it, because I can erase all the private date anytime I want with "clear private data".
How?
How can i do this? i cant see it in the tool tabs? Am i having a virus in my browser?
Re: How?
Make sure that you're using either Firefox 3.5 or 3.5. You can see the version number in the About window accessible from the Help menu.
Thanks for your answer.
Thanks for your answer.
Access Private browsing history / history?
Hi I was wondering if there is anyway I can access/ recall the private browsing history without having to purchase special sofware? Cheers All
Re: Access Private browsing history / history?
No, the browsing history inside the private browsing mode is not recorded, and there is no way to retrieve that information later. This is the main point behind the private browsing mode feature.
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Clarification
In your description above, you say:
This action discards all of the data from your private session, and will restore your non-private browsing session, just like it was before entering the Private Browsing mode.
This leads me to believe that data is at some point written to disk and then later "deleted". Can you clarify if this is, or is not, the case. If data is written during PB and then erased at the end, then this is no different than Clear Private Data function, and is not secure since the files can be recovered. I understood PB to mean that no data was ever written to disk (unless you download or open a file using a native application).
Please clarify.
Thanks
Re: Clarification
No, the data you're talking about is never written to disk during the private browsing mode. By "discarding" I meant that Firefox clears them from main memory.
This way if your browser crashes during a private browisng session (or there is a power outage, or any other reason why Firefox would not be able to shut down clearly), then no traces of your browsing would remain on the hard disk of your computer.
Pingback
[...] preview release intended for developer testing and community feedback. New features include a private browsing mode, new functions that make it easy to remove specific portions of web history, a new javascript [...]
Active downloads are cancelled when exiting private browsing
When you quit private browsing, it's easy to forget if you have any downloads in progress. Any downloads which are in progress get canceled as well.
It would be useful to have some sort of warning when you try to quit private browsing:
eg.
"You have active downloads in progress. Are you SURE you want to quit private browsing at this time?"
Re: Active downloads are cancelled when exiting private browsing
We actually do show such a warning if the download is not resumable. If it is, we just pause it silently, and restart it when you leave the private browsing mode.